Apparatus and method for sterilizing container closures

ABSTRACT

An apparatus ( 1 ) for sterilizing container closures comprises a conduit ( 2 ) defining a passage for the closure and having a wall ( 3 ) surrounding the passage, spraying means ( 4 ) for injecting inside the conduit ( 2 ) a sterilization fluid heated and vaporized, drying means for introducing hot air in the conduit ( 2 ) and means for heating the wall ( 3 ) of the conduit ( 2 ) operatively coupled thereto. A method for sterilizing container closures transported inside a conduit ( 2 ) having a wall ( 3 ) defining internally a passage for the closures comprises the steps of injecting inside the conduit ( 2 ) a sterilization fluid heated and vaporized, introducing hot air in the conduit ( 2 ) for drying the closures and heating the wall ( 3 ) of the conduit ( 2 ) by transferring heat directly to the conduit wall ( 3 ).

TECHNICAL FIELD AND BACKGROUND ART

The present invention relates to an apparatus and a method forsterilizing container closures.

As generally known, in the food industry and in particular in the fieldof aseptic filling of containers with beverages and in the field ofaseptic food packaging, there exists a need to sterilise the containersboth internally and externally before they are filled.

Sterilisation is generally achieved using chemical agents, e.g. hydrogenperoxide, which can be used on surfaces of every type, such as paper,plastic, metal or organic materials.

To ensure that filling takes place in aseptic conditions it is necessaryto sterilise not only the containers but also their closures, forexample caps or stoppers, which serve to seal the containers at the endof the filling process.

In this light, known apparatuses for sterilizing container closurescomprise a conduit having a wall defining internally a passage for theclosures.

Hence, said known apparatus defines inside the conduit a closed volumehaving a controlled aseptic atmosphere. Said known apparatus comprisesspraying means for injecting inside the conduit a sterilization fluid(i.e. a chemical agent) heated and vaporized, and drying means forintroducing hot air in the conduit.

The drying means have the function of eliminating the sterilizationfluid condensed on the closures, before the closures themselves exit theapparatus.

It is noteworthy to observe that the sterilization fluids which arecommonly used in these apparatuses are chemically active when theirtemperature is above a threshold value (activation value).

For this reason, the sterilization fluid is heated before it is injectedin vaporized fashion inside the conduit. In this light, the apparatuscomprises a device for heating and vaporising the sterilization fluid,for instance as described in patent application WO2006128884 of the sameapplicant.

Because the whole volume inside the conduit must be aseptic, the needarises of securing that the whole amount of fluid present inside theconduit be at a temperature above the activation value.

Thus, it is desirable that also the sterilization fluid that iscondensed on the internal surface of the wall of the conduit be active(i.e. above the activation threshold).

For this purpose, in the operation of the sterilization process, theenthalpy of the process fluids (i.e. the sterilization fluid and thedrying air) is regulated taking account of the fact that a portion ofsaid enthalpy is needed to heat the conduit wall.

Therefore, in the known apparatus the process fluids (i.e. thesterilization fluid and the drying air), which are oriented towards theclosures in order to treat them as described above, heat the fluidfilling the volume internal to the conduit 2, and thus indirectly heatthe conduit wall 3.

However, this known apparatus has the following drawbacks.

First of all, in the known apparatus the process fluids are notoptimized for the treatment (i.e. sterilization) of the closures; infact, the use of a portion of the enthalpy of the process fluids toobtain the heating of the conduit wall is a waste of energy.

In addition, a use of process fluids which is excessive with regard tothe sterilization purposes (excessive with regard to either the flowrate or the temperature of the process fluids themselves) determines arisk of damaging the closures; in fact, en excessive heat is transferredto the closures; in particular, the temperature of the process fluids istoo high.

A further problem arises in relation to the need of getting rid of theexhaust fluids which exit from the conduit. In fact, the exhaust, fluidsexiting from the conduit would flow into the environment surrounding theconduit, if the exhaust fluids were not captured.

In this light, it is noteworthy to observe that the standards fix thethreshold values (which must not be exceeded) for the concentration ofthe exhaust fluids in the environment of the sterilization conduit (infact, said environment is itself kept aseptic).

Therefore, the sterilization apparatus comprises a system for theextraction of the exhaust fluids, from the conduit, in such a way thatthey do not flow in the environment.

In the known apparatus, an exhaust tube is provided, which is connectedto a suction pump at one end and directly to the conduit at the oppositeend. In this way, a suction force is directly applied to the volumeinside the conduit.

This technical solution has the drawback to generate undesired flows ofthe process fluids inside the conduit, thus altering the distribution ofthe process fluids inside the conduits.

Therefore, the distribution of the process fluids inside the conduit isnot optimized because it is affected by the suction force applied by thesystem for extracting the exhaust fluids.

DISCLOSURE OF THE INVENTION

An object of the present invention is to eliminate the aforesaiddrawbacks and to make available an apparatus and a method forsterilizing container closures, which is particularly efficient andoptimizes the use of the process fluids with respect to thesterilization of the closures.

An additional object is to make available an apparatus and a method forsterilizing container closures which has reduced operation costs.

Said objects are fully achieved by the apparatus of the presentinvention, which is characterised by the content of the claims set outbelow.

BEST MODE FOR CARRYING OUT THE INVENTION

These and other features shall become more readily apparent from thefollowing description of a preferred embodiment, illustrated purely byway of non limiting example in the accompanying drawing tables, inwhich:

FIG. 1 shows the apparatus according to the present application, inperspective view;

FIG. 2 shows the apparatus of FIG. 1, in a different perspective view;

FIG. 3 shows an enlarged view of the portion A of FIG. 2;

FIG. 4 shows the apparatus of FIG. 1, in a further perspective view;

FIG. 5 shows an enlarged view of the portion B of FIG. 4;

FIG. 6 shows a functional diagram pertaining to the method according tothe present patent application;

FIG. 7 shows the apparatus according to the present applicationincluding the system for the extraction of the exhaust fluids, inlateral view;

FIG. 8 shows an enlarged view of a first operative portion of theapparatus of FIG. 7;

FIG. 9 shows the portion of FIG. 8, in a perspective view;

FIG. 10 shows an enlarged view of a third operative portion of theapparatus of FIG. 7;

FIG. 11 shows the portion of FIG. 10, in a perspective view;

FIG. 12 shows an enlarged view of portion C of FIG. 7;

FIG. 13 shows an internal portion of the apparatus of FIG. 7.

With reference to the Figures, the numeral 1 globally designates anapparatus for sterilizing container closures, such as caps or stoppers,which serve to seal the containers and are applied to the containers atthe end of the filling process.

The apparatus 1 comprises a conduit 2 which defines a passage for theclosures.

The conduit 2 has at least one wall 3; in particular, the conduit 2 hasa lateral wall 3 which surrounds the passage for the closures.

The conduit 2 has, in the illustrated example, a rectangular section;accordingly, the wall 3 comprises four faces, each having substantiallyflat shape.

In addition, the conduit 2 is preferably arranged along a longitudinaldirection.

However, such a configuration of the conduit 2 is not essential; infact, the conduit 2 may have a different shape, for example a tubehaving a wall 3 with circular section and arranged on a curved path.

Inside the conduit 2 a conveyor is arranged (not shown in the figures)to transport the closures form an inlet to an outlet of the conduit 2itself. Said inlet and outlet correspond to the inlet and outlet of theapparatus 1. The apparatus 1 receives (singularly) at the inlet theclosures to be sterilized and makes available the same closures at theoutlet after their sterilization.

The closures inside the conduit 2 are preferably arranged with theirbottom wall face up and their concave portion face down.

The apparatus 1 also comprises a plurality of nozzles 4 coupled to theconduit 2 for injecting a sterilization fluid inside the conduit 2.

The apparatus is also provided with a system for heating and/orvaporizing the sterilization fluid, in order to feed the nozzles 4 withsterilization fluid which is heated above the activation temperature forthat fluid and is vaporized. Such a system, not shown in the figures, isdescribed in patent application WO2006128884 of the same applicator,which is here incorporated by reference.

Therefore, the nozzles 4, together with said system (i.e. the system forheating and vaporizing the sterilization fluid), define spraying meansfor injecting inside the conduit 2 a sterilization fluid heated andvaporized.

Said sterilization fluid is preferably Vapour of Hydrogen Peroxide(VHF).

In particular, the spraying means comprises a first delivery pipe 5,which is arranged inside the conduit 2. The first delivery pipe 5 isprovided with a plurality of holes along its length, which define thenozzles 4. The first delivery pipe 5 is fed with the sterilization fluid(heated and vaporized as described above) at one of its ends and isclosed at an opposite end (said closed end is indicated with thereference number 6 in the figures).

Furthermore, the apparatus 1 comprises drying means for introducing hotair in the conduit, for the purpose of removing the sterilization fluidcondensed on the closures.

In the preferred embodiment illustrated in the figures, the drying meanscomprises a second delivery pipe 7, which has a structure similar tothat of the first delivery pipe 5 (i.e. is arranged inside the conduit 2and has a closed end) but is fed with heated air (or any inert gas).

Therefore, the drying means is configured to provide a flow of hot airable to intercept the closures passing inside the conduit 2. Said airtubes are connected to a source of heated air, and aseptic filters areinserted downstream the source of heated air, to secure that theenvironment inside the conduit 2 is kept aseptic. The drying means arecoupled to the conduit 2 substantially downstream with respect to thespraying means, in the direction of movement of the closures inside theconduit 2.

In this light, it is important to observe that the conduit 2 preferablydefines three operative portions, which are arranged consecutively alongthe path followed by the closures in their movement inside the conduit2.

A first operative portion is provided with the first delivery pipe 5(and thus with the nozzles 4), i.e. it is the portion where the sprayingmeans is active.

A third operative portion is provided with the second delivery pipe 7,i.e. it is the portion where the drying means is active.

A second operative portion, intermediate between the first and thesecond operative portion, is a portion where neither the spraying meansnor the drying means is directly active on the closures (i.e. neitherthe first delivery pipe 5 nor the second delivery pipe 7 is arranged inthe second operative portion of the conduit 2).

In addition, the apparatus 1 originally comprises means for heating thewall 3 of the conduit 2 (i.e. the wall 3 surrounding the passage for theclosures to be sterilized), which are operatively coupled thereto.

Said heating means are preferably coupled to at least one of the facesof the wall 3 of the conduit 2 on its whole length, i.e. along the pathfollowed by the closures in their movement inside the conduit 2. Hence,the heating means are coupled to at least one face of the wall 3 of allof the three operative portions of the conduit 2 described above.

This feature has the advantage that length of the second operativeportion of the conduit 2 may be set to a desired value (said lengthhaving an influence on the overall performance of the apparatus 1 andthus being a parameter to be optimized) and the flow of the processfluids (i.e. sterilizing fluid and drying air) set independently at adesired optimized value, the wall 3 of the conduit 2 (including thesecond operative portion of the conduit 2) being heated independentlywith respect to the process fluids.

In the preferred embodiment of the apparatus 1, illustrated in thefigures, said means for heating the wall 3 of the conduit 2 comprises aheating layer 8 attached to the external surface of the wall 3. Thislayer 8 is provided with a plurality of electric resistors.

Thus, the electric resistors are associated to the heating layer 8attached to said external surface of the wall 3.

In particular, said layer 8 comprises a plurality of stripes having anadhesive surface to be coupled to the faces of the wall 3 of the conduit2. The electric resistors are associated to said stripes, according to aknown technique.

Therefore, at least an electrical resistor is directly coupled to anexternal surface of the wall 3 of the conduit 2, providing a heater ofthe wall 3 itself directly coupled thereto. The heater (the electricresistors) is connected to an electric power source 9, and transfersdirectly to the wall 3 of the conduit 2 the heat generated by virtue ofJoule effect.

In particular, the apparatus 1 comprises a plurality of electricresistors connected in parallel to the electric power source 9.

It is noteworthy to observe that said power source is independent fromsaid spraying means and drying means (i.e. the sterilization fluid andthe drying air have are not used for heating the conduit wall).

The latter feature is particularly important, because it allows to heatthe conduit wall 3 without interfering with the sterilization process,which is regulated by the process fluids (i.e. the sterilization fluidand the drying air).

It also has to be noted that the heater is coupled to the conduit 2 insuch a way as to maximize the portion of wall 3 where heat is exchanged.

In the preferred embodiment illustrated in the figures, the conduit wall3 has a to transparent portion 10 for inspecting the interior of theconduit 2 (and in particular the closures conveyed inside the conduit2).

In this light, said heater (i.e. the layer 8 provided with theelectrical resistors) is operatively active on the whole remainingportion of the conduit wall 3.

It is noteworthy to observe that the means for heating the wall 3 of theconduit 2, according to an alternative embodiment not shown in thefigures, comprises a duct (or a plurality of ducts) wherein heatingfluid is pumped, the duct being arranged in contact with the conduitwall 3, thus providing a heat exchanger able to increase the temperatureof the conduit wall. Said heating fluid may be taken form any heatingsource (preferably independent from the process fluids) and does notrequire to be filtered, since it does not come into contact with theaseptic environment internal to the conduit 2.

According to a further aspect of the present invention, the apparatus 1is provided with a system for controlling the temperature of the wall 3(provided with the heating means). The aim of this system is to maintainthe wall temperature at a desired value avoiding any waste of energy. Afurther aim of this system is to monitor the means for heating theconduit 2, detecting possible faults and bad functioning.

In this light, the apparatus 1 comprises at least a sensor 11 (e.g. athermocouple) coupled to the wall 3 of the conduit 2 to detect thetemperature thereof, and an electronic card 12, which constitutescontrol means connected to the power source 6 and to the sensor 11 toregulate retroactively the power transferred to the heater (andtherefore the heat transferred to the wall 3), in such a way that thetemperature of the conduit wall 3 has a desired value (i.e. a referencevalue Tref).

Said desired value is not lower than the activation value of temperatureof the chemical agent used as sterilization fluid. For example, saiddesired value for the temperature of the conduit wall ranges fromapproximately 50° C. to approximately 130° C., when VIP is used assterilization fluid.

Preferably, the apparatus 1 comprises a plurality of sensors 11 coupledto different points of the conduit wall 3, to detect correspondingtemperature values of the conduit wall. These detection points arepreferably longitudinally spaced along the whole length of the conduitwall 3; more preferably, at least a sensor 11 is provided incorrespondence to each of the three operative portions of the conduit 2.

In addition, each sensor 11 is preferably coupled to a portion of thewall 3 wherein a corresponding heater is coupled (where a plurality ofheaters, each e.g. formed by a plurality of resistors, are arranged inparallel).

This is particularly important in combination with the fact that themeans for heating the wall 3 comprises a plurality of heaters connectedin parallel and arranged along the conduit aligned longitudinally.

In fact, in this way it is possible to detect if a portion of the wall 3has a temperature lower than the rest of the wall (and maybe lower thanthe activation value). This may be caused by a fault of one of theheaters (e.g. one of the panels constituting the layer 8 of electricresistors).

In this case, the control means are configured to regulate the powertransferred to the other heaters (the ones which are working properly)to maintain the desired temperature of the wall 3 (thus maintaining thewall 3 at a uniform and constant temperature), and at the same time foractivating alert means in response to the detected fault condition.

It is noteworthy to observe that the power source 9 preferably comprisesa source of continuous voltage (e.g. any alternate power source coupledto a rectifier or any other alternative solution) connected to aconverter 13 defining a module for a PWM modulation of a voltage appliedto the resistors.

In this light, the control means 12 are connected to said converter 13in order to drive it in response to the result of the comparison betweenthe reference temperature value (Tref) and the temperature valuesdetected by the sensors 11 (as schematically shown in FIG. 6).

The apparatus 1 also comprises a system for capturing the exhaust fluidswhich exit from the conduit 2.

Such a system comprises exhaust openings 14 consisting of outletsdefined in the upper portion of the wall 3 and preferably extendingupwards.

These exhaust openings 14 cooperate with corresponding suction hoods 15defined in a exhaust tube 16, wherein a suction pump is preferablyinserted.

According to an alternative embodiment, the suction pump is substitutedwith an exhaust tube 16 defining a vertical column in correspondence tothe exhaust openings 14, in such a way to provide an adequate naturaldraught.

It is noteworthy to observe that the exhaust opening 14 is arranged at apredetermined distance from the lower end of the correspondent suctionhood 15; therefore, the exhaust tube 16 is not directly connected to theconduit 2.

Preferably, a plurality of exhaust openings 14 and correspondent suctionhoods 15 is provided; in the illustrated embodiment three openings 14and correspondent suction hoods 15 are provided, each suction hood 15being arranged in correspondence of a respective operative portion ofthe conduit 2.

Preferably, the suction hood 15 has a section which is larger than thesection of the correspondent exhaust opening 14.

Such a feature allows to provide a step of capturing the exhaust fluidsexiting from the exhaust opening 14 of the conduit 2 and shiftinglaterally while moving upwards.

In this way, the exhaust fluids present inside the exhaust opening 14are captured by way of a suction principle analogous to that of a hooddraught (e.g. the draught of a hood provided in a professional kitchento capture the fumes produced by the cooking).

In addition, each suction hood 15 is provided with means for adjustingthe effective section of the suction hood 15 itself.

These means for adjusting the effective section of the suction hood 15(illustrated in FIG. 13) comprises preferably a fist flange 17 and asecond flange 18 arranged inside the suction hood 15 in contact witheach other and in such a way to be rotated one with respect to theother.

Said fist flange 17 and second flange 18 define apertures 19 whichincrease or decrease their overlap as a function of the reciprocalangular position of the fist flange 17 and second flange 18.

Thus, when the overlap of corresponding apertures 19 of the flanges 17and 18 is minimum, the effective section of the suction hood 15 isaccordingly minimized; likewise, when the overlap of correspondingapertures 19 of the flanges 17 and 18 is maximum, the effective sectionof the suction hood 15 is accordingly maximized.

Alternatively to or additionally to said means for adjusting theeffective section of the suction hood 15, means are provided (notillustrated because itself known) to vary the power applied to thesuction pump inserted in the exhaust tube 16, with the possibility tocontrol said means (e.g. the pump may be driven by an electric powersource through an inverter controlled by an electronic card).

It is noteworthy to observe that such a distance (between the upper endof the exhaust opening 14 and the lower end of the correspondent suctionhood 15), the effective section of the suction hood 15 and the ratiobetween the section of the upper end of the exhaust opening 14 and thesection of the lower end of the correspondent suction hood 15 (theformer section being smaller than the latter section) constituteparameters which are set in order to minimize the effect of the systemfor extracting exhaust fluids from the conduit 2 on the distribution ofthe fluids contained inside the conduit.

In such a way, the fluid-dynamic distribution of the process fluidinside the conduit 2 is not affected by the extraction of the exhaustfluids; in fact, the exhaust fluids are captured by way of a draughtprinciple, and no suction force is directly applied to the fluidcontained inside the conduit 2.

Such a result improves the performance of the apparatus, because itavoids undesired flows of process fluids inside the conduit 2, and thusit allows to control the distribution of the process fluids inside theconduit 2 optimizing their effect on the closures.

It is further object of the present invention a method for sterilizingcontainer closures transported inside a conduit 2 haying a wall 3defining internally a passage for the closures.

Said method comprises the following steps:

-   -   injecting inside the conduit 2 a sterilization fluid heated and        vaporized (VHP);    -   introducing hot air in the conduit for drying the closures,    -   heating the wall 3 of the conduit 2 by transferring heat        directly to the conduit wall.

It is noteworthy to observe that the heating step entails the heatingthe wall 3 on the whole length of the conduit 2, thus heating all of thethree operative portions of the conduit 2.

Preferably, in the heating step, the heat is transferred to the wall 3from a heat source which is independent from the process fluids (i.e.said sterilization fluid and said drying air).

In particular, the heating step entails the transmission of energy froma power source independent from said spraying means and drying means toat least a heater directly coupled to an external surface of the conduitwall 3.

Preferably, said heater is an electrical resistor (or a layer 8attachable to the wall 3 and provided with a plurality of resistorsconnected with each other) and said power source is an electric powersource; in this light, the heating step entails the transmission ofelectrical energy from the electrical power source to said at least aheater.

The method further comprises a step of detecting at least a value of thetemperature of the conduit wall 3, and a step of regulatingretroactively the power transferred to the heater, in such a way thatthe temperature of the conduit 2 wall 3 has a desired value (asdescribed above with respect to the apparatus 1). Preferably, thesterilization fluid is VHP and said desired value for the temperature ofthe conduit wall ranges from approximately 50° C. to approximately 130°C.

Said detection step preferably entails the coupling of a plurality ofsensors 11 to different points of the conduit wall 3, to detectcorresponding temperature values of the conduit wall. More preferably,the detecting step entails the detection of at least a temperature valuein correspondence of each of the three operative portions of the conduit2.

In addition, preferably the heater is defined by layers 8 comprisingelectrical resistors and attached to the external surfaces of theconduit 2 wall 3.

In this light, said regulating step entails a PWM modulation of avoltage applied to the resistor.

It is noteworthy to observe that the heating step, according to analternative embodiment, comprises a step of pumping a heating fluid(i.e. a hot fluid) through a duct (or a plurality of ducts) arranged incontact with the conduit wall 3, thus providing a heat exchange (fromthe heating fluid to the wall 3) in order to increase the temperature ofthe wall 3 of the conduit 2.

In fact, the heat transferred in the heating step may be transferred bya conduction principle (heat transferred to the wall 3 e.g. fromelectric resistors directly coupled to the wall itself) or by convectionprinciple (heat transferred to the wall 3 e.g. from a heating fluidconveyed along a surface, and in particular the external surface, of thewall itself).

The method according to the present application further comprises a stepof extracting exhaust fluids from the conduit 2.

Such an extracting step entails a step of arranging a plurality ofconsisting of outlets defined in the upper portion of the conduit 2 wall3 and extending upwards (defining exhaust openings 14), cooperating withcorresponding suction hoods 15 defined in a exhaust tube 16, wherein asuction pump is inserted (according to the description above of theapparatus 1).

Hence, the extracting step consists of capturing the exhaust fluids byway of a draught principle.

The extracting step further comprises a step of adjusting the effectivesection of the suction hoods 15.

Such an adjusting step entails preferably the rotation of a fist flange17 with respect to a second flange 18, these flanges being arranged incontact with each other inside the suction hood 15, in such a way to berotatable one with respect to the other. Said fist flange 17 and secondflange 18 define apertures 19 which increase or decrease their overlapas a function of the reciprocal angular position of the fist flange 17and second flange 18 (according to the description above of theapparatus 1).

It is noteworthy to observe the upper end of the exhaust opening 14 isarranged at a predetermined distance from the lower end of thecorrespondent suction hood 15.

Such a distance (between the upper end of the exhaust opening 14 and thelower end of the correspondent suction hood 15), the effective sectionof the suction hood 15 and the ratio between the section upper end ofthe exhaust opening 14 and the section of the lower end of thecorrespondent suction hood 15 (the former section being smaller than thelatter section) constitute parameters which are set in order to minimizethe effect of the system for extracting exhaust fluids from the conduit2 on the distribution of the fluid contained inside the conduit.

Hence, the method according to the present application further comprisesa step of adjusting these parameters to minimize the effect of thesystem for extracting exhaust fluids from the conduit 2 on thedistribution of the fluid contained inside the conduit 2. withoutmodifying any fluid-dynamics equilibrium.

The invention described above provides the following advantages.

The apparatus and method for sterilizing closures according to thepresent invention allow to maintain the wall 3 of the conduit 2 at adesired temperature value (above the activation value of thesterilization fluid injected in the conduit) independently on theoperation of the process fluids (i.e. the sterilization fluid and thedrying air injected in the conduit 2).

Therefore, the temperature and the flow rate of the process fluids areoptimized for the sterilization of the closures, thus avoiding waste ofenergy and any risk of damaging the closures.

In addition, the apparatus and method for sterilizing closures accordingto the present invention allow an optimization of the energy used toheat the conduit wall and provide a control system able to achieve anautomatic regulation and detection (also providing alert signals) ofpossible faults in the heating of the conduit wall.

The apparatus and method for sterilizing closures according to thepresent invention further allow to provide a uniform and constanttemperature of the conduit wall, thanks to said control system incombination with the presence of a plurality of sensors coupled atdifferent points of the conduit wall for multiple temperature detection.

A further advantage is to improve the performance of the apparatusavoiding undesired flows of process fluids inside the conduit 2, andthus allowing to control the distribution of the process fluids insidethe conduit 2 optimizing their action on the closures.

Such a result is possible because, in the step of extracting the exhaustfluids, the exhaust fluids are captured by way of a draught principle(hence no suction force is directly applied to the fluid containedinside the conduit 2), thus allowing the fluid-dynamic distribution ofthe process fluid inside the conduit 2 not being affected by theextraction of the exhaust fluids.

The invention claimed is:
 1. Apparatus (1) for sterilizing containerclosures, comprising: a conduit (2) defining a passage for the closuresand having a wall (3) surrounding the passage, the conduit (2) defininga spraying operative portion and a drying operative portion, thespraying operative portion and the drying operative portion beingnonoverlapping; spraying means (4) for injecting inside the conduit (2)within the spraying operative portion a sterilization fluid heated andvaporized; drying means for introducing hot air inside the conduit (2)within the drying operative portion; means for heating the wall (3) ofthe conduit (2) operatively coupled thereto; said means for heating thewall (3) of the conduit (2) comprising at least a heater (8) coupled toan external surface of the wall (3) and connected to a power source (9)independent from said spraying means and said drying means, the meansfor heating the conduit (2) wall (3) being coupled at least to thespraying operative portion and to the drying operative portion. 2.Apparatus according to claim 1, wherein said heater (8) is an electricresistor and wherein the power source (9) is an electric power source(9).
 3. Apparatus as claimed in claim 2, wherein said means for heatingthe wall of the conduit comprises a plurality of electric resistorsconnected in parallel to said electric power source (9).
 4. Apparatusaccording to claim 1, wherein the conduit (2) wall (3) has a transparentportion (10) for inspecting the interior of the conduit (2), and whereinsaid means for heating the wall (3) are configured for being operativelyactive on the whole remaining portion of the conduit (2) wall (3). 5.Apparatus according to claim 1, comprising: at least a sensor (11)coupled to the conduit (2) wall (3) to detect the temperature thereof;control means (12) connected to the means for heating the wall (3) andto the sensor (11), to regulate retroactively the heat transferred tothe wall (3), in such a way that the temperature of the conduit wall (3)has a desired value.
 6. Apparatus according to claim 1, comprising means(15,16) for capturing exhaust fluids from the conduit (2) having atleast a suction hood (15) arranged over a corresponding exhaust opening(14) defined in the conduit (2) and facing upwards, at a predetermineddistance thereto.
 7. Apparatus according to claim 6, wherein the sectionof said suction hood (15) is larger than the section of thecorresponding exhaust opening (14), to provide a capturing of theexhaust fluids by way of a draught effect.
 8. The apparatus according toclaim 1, the conduit (2) defining an intermediate operative portionlocated intermediate between the spraying operative portion and thedrying operative portion, wherein the means for heating the conduit wallis also coupled to the intermediate operative portion.
 9. Method forsterilizing container closures transported inside a conduit (2) having awall (3) defining a passage for the closures, the conduit (2) defining aspraying operative portion and a drying operative portion, the sprayingoperative portion and the drying operative portion being nonoverlapping,the method comprising the following steps: injecting, by spraying means,inside the conduit (2) within the spraying operative portion asterilization fluid heated and vaporized; introducing, by drying means,hot air inside the conduit (2) within the drying operative portion, fordrying the closures; heating the wall (3) of the conduit (2) bytransferring heat directly to the spraying operative portion and to thedrying operative portion of the conduit wall (3); the heating stepincluding the transmission of energy from a power source independentfrom said spraying means and said drying means to at least a heater (8)directly coupled to an external surface of the conduit wall (3). 10.Method according to claim 9, wherein said heater is an electricalresistor and said power source is an electric power source, the heatingstep including the transmission of electrical energy from the electricalpower source to the heater.
 11. Method according to claim 10, comprisinga step of detecting at least a value of temperature of the conduit (2)wall (3), and a step of regulating retroactively the heat transferred tothe wall, in such a way that the temperature of the conduit wall (3) hasa desired value.
 12. Method according to claim 9, comprising a step ofdetecting at least a value of temperature of the conduit (2) wall (3),and a step of regulating retroactively the heat transferred to the wall,in such a way that the temperature of the conduit wall (3) has a desiredvalue.
 13. Method according to claim 9, comprising a step of capturingexhaust fluids exiting from the conduit (2), said capturing phaseincluding a step of arranging at least a suction hood (15) over acorresponding exhaust opening (14) extending upwards from the conduit(2), at a predetermined distance thereto, to capture the exhaust fluidsfrom the conduit (2) by way of a draught effect.
 14. Method according toclaim 13, wherein the section of the suction hood (15) is larger thanthe section of the corresponding exhaust opening (14), to provide a stepof capturing the exhaust fluids exiting from the exhaust opening (14) ofthe conduit (2) and shifting laterally while moving upwards.